The Great Detective Race: The Boxcar Children Mysteries, Book 115

A local radio station is holding the Great Detective Race, and the Boxcar Children have entered the contest! They solve riddles and search all over town for clues leading to the grand prize. But when some of the clues turn out to be fake, it's clear that someone is playing unfairly! Who could be trying to ruin the raceamp;mdash;and why?